Numerical simulation of flow and heat transfer characteristics in Solar Enhanced Natural Draft Dry Cooling Tower

A Solar Enhanced Natural Draft Dry Cooling Tower (SENDDCT) is a Natural Draft Dry Cooling Tower that uses solar energy to enhance the cooling performance and lower the operating cost for a power plant. In this paper, a three-dimensional numerical stimulation is developed by using FLUENT to investigate the effects of the following operating parameters on the thermal performance of the SENDDCT: the collector diameter, ambient temperature and the types of heat exchanger layout. The numerical simulation results reveal that the heat transfer rate is proportional to collector diameter, but is inversely proportional to the ambient temperature. Specifically, decreasing the ambient temperature from 305.15 K to 283.15 K has result in an increase of almost 104.2 MW in heat transfer rate. For a fixed heat exchanger area, the heat rejection of the SENDDCT decreases with an increasing coverage ratio for a given “unit coverage ratio” defined in this paper. It is found that stronger vortices are generated at the back of heat exchangers due to the introduction of the blockage units. Using smaller heat exchanger and blockage units can weaken vortices and enhance cooling performance.